A wide assortment of semiconductor devices operate in conjunction with various forms of electromagnetic energy. Magnetoresistive random access memory (MRAM) devices, for example, typically include memory cells incorporating ferromagnetic films that are programmed using localized electromagnetic fields. Stray magnetic fields of significant strength generated external to the memory cell may cause operational errors—e.g., errors arising during the read and/or write operations. It is therefore desirable to shield such cells and other susceptible regions from external magnetic fields.
Prior art methods of shielding such components are unsatisfactory in a number of respects. For example, metals with known shielding properties such as PERMALLOY (80Ni/20 Fe) and MUMETAL (80Ni/13.5Fe/4.9Mo/0.5Mn/0.3Si) may be deposited over critical electromagnetic-field-susceptible devices. Such materials, however, which are often formed using an electroplating process, tend to give rise to high residual stresses. NiFe alloys, for example, generate significant tensile stresses. These stresses can result in significant wafer warpage, die-level fractures, deformation, and/or interfacial failure. Since shielding of semiconductor devices requires relatively thick films, the stress effects are significant enough that they can interfere with subsequent processing steps such as backgrinding, dicing, and the like. Additives may be supplied in the electroplating bath formulations to decrease the resulting internal stress of the plated alloy. However, such techniques have met with little success in substantially eliminating such stresses.
Accordingly, it is desirable to provide structures and methods for shielding susceptible semiconductor devices from unwanted electromagnetic fields, while reducing residual stresses. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.